Title

Characterization of ionomer solutions in non-polar solvents

Date of Completion

January 1997

Keywords

Chemistry, Polymer|Engineering, Materials Science|Plastics Technology

Degree

Ph.D.

Abstract

The effect of specific interactions on polymer solution properties was studied by examining the aggregation behavior of ionomers in non-polar solvents. Temperature-concentration phase diagrams of acid form of sulfonated polystyrene (HSPS) solutions in decalin were determined using a light scattering technique. Upper Critical Solution Temperature (UCST) type phase behavior was observed and the UCST's increased with increasing sulfonation level. This indicated that aggregation of HSPS molecules was a major factor in determining the solubility of these ionomers in non-polar solvents.^ The association of sulfonic acid groups of HSPS in solution due to hydrogen bonding was investigated using dynamic light scattering. CONTIN analysis of the field autocorrelation functions yielded a single relaxation mode for low HSPS concentration (at temperatures away from the cloud point), and two relaxation modes for higher concentrations. The fast relaxation mode was attributed to the presence of single chains or small sized aggregates of HSPS, and the slow relaxation mode to the presence of large multi-chain aggregates. In a narrow range of temperature above the cloud point, the slow relaxation mode diffusion coefficient decreased drastically indicating that extensive aggregation occurred close to the phase boundary. This was substantiated by the appearance of a slow relaxation mode in the low concentration solutions at temperatures very close to the phase boundary. The extensive aggregation then provides the driving force for phase separation at temperatures that are much higher than the cloud point temperatures of the precursor polystyrenes from which the HSPS were synthesized. ^